KR20230012791A - Non-aqueous electrolyte, and lithium secondary battery comprising the same - Google Patents

Abstract

The present invention relates to a non-aqueous electrolyte including: lithium salt; an organic solvent; and a compound represented by a specific formula. Provided is a non-aqueous electrolyte capable of improving lithium ion transport characteristics, electrochemical stability, and battery durability. A lithium secondary battery has excellent lifespan characteristics. Due to the excellent lithium ion transport characteristics, resistance is low and output characteristics can be improved.

Description

Non-aqueous electrolyte, and a lithium secondary battery containing the same

The present invention relates to a non-aqueous electrolyte and a lithium secondary battery including the same.

Recently, personal IT devices and computer networks have been developed due to the development of the information society, and as the dependence on electrical energy in the society as a whole has increased accordingly, the development of battery technology for efficiently storing and utilizing electrical energy is required.

In particular, as interest in solving environmental problems and realizing a sustainable recycling-type society has emerged, research on electrical storage devices such as lithium ion batteries and electric double-layer capacitors has been extensively conducted. Among them, lithium secondary batteries are in the limelight as a battery system with the highest theoretical energy density among battery technologies.

The lithium secondary battery is largely composed of a positive electrode composed of a transition metal oxide containing lithium, a negative electrode capable of storing lithium, an electrolyte serving as a medium for delivering lithium ions, and a separator, and in the case of the double electrolyte, the stability of the battery ( As it is known as a component that greatly affects stability and safety, etc., many studies are being conducted on it.

In this regard, a non-aqueous electrolyte containing a lithium salt and an organic solvent is generally used as an electrolyte for a lithium secondary battery, and a carbonate-based organic solvent is used as the organic solvent. At this time, when exposed to a high temperature or high voltage, the carbonate _- based organic solvent is easily decomposed at the interface of the electrode (anode or cathode) and cannot function as an electrolyte solution. This causes the volume of the battery to increase and the durability of the battery to deteriorate. In particular, when a lithium transition metal composite oxide containing a large amount of Ni is used as a cathode active material, or when a lithium secondary battery requiring a high voltage is used, this problem is further intensified.

Therefore, there is an urgent need to develop a non-aqueous electrolyte solution for a lithium secondary battery capable of improving lithium ion transport characteristics, electrochemical stability, battery durability, and the like.

US Patent Publication No. 2018-0316061 discloses an amide-based electrolyte battery, but failed to suggest an alternative to the above problems.

US Patent Publication No. 2018-0316061

One object of the present invention is to provide a non-aqueous electrolyte capable of improving lithium ion transport characteristics, electrochemical stability and battery durability.

In addition, another object of the present invention is to provide a lithium secondary battery including the above-described non-aqueous electrolyte.

The present invention is a lithium salt; organic solvents; And a compound represented by Formula 1;

[Formula 1]

In Formula 1, R ₁ and R ₂ are each independently a substituent selected from an alkyl group having 1 to 10 carbon atoms and an aryl group having 6 to 14 carbon atoms, and R ₃ , R ₄ , R ₅ , and R ₆ are each independently A substituent selected from the group consisting of hydrogen, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, and an aryl group having 6 to 14 carbon atoms, wherein R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ In at least one substituent of, at least one hydrogen is substituted with a halogen element selected from the group consisting of F, Br, Cl and I.

In addition, the present invention is a negative electrode; an anode facing the cathode; a separator interposed between the cathode and the anode; And the aforementioned non-aqueous electrolyte; provides a lithium secondary battery comprising a.

The non-aqueous electrolyte solution according to the present invention includes a lithium salt; organic solvents; And by including a compound represented by a specific formula, it is characterized in that lithium ion transfer characteristics, electrochemical stability and battery durability can be improved. Specifically, the compound included in the non-aqueous electrolyte according to the present invention has a higher melting point than conventional carbonate-based compounds, has stable electrochemical properties, and does not generate gaseous by-products such as CO ₂ even when decomposed, so that it can be used when driving a lithium secondary battery. It is possible to prevent an increase in volume and decrease in battery durability. In addition, the compound included in the non-aqueous electrolyte according to the present invention can form a coordination structure with lithium ions by including a halogen element such as F, Br, Cl, I, etc. in the compound, thereby improving lithium ion transfer performance, It is possible to increase the energy level of the HOMO (Highest Occupied Molecular Orbital) of the compound, so that oxidation stability can be remarkably improved, by-product formation by decomposition reaction is prevented, and reductive decomposition easily occurs, thereby forming a solid electrolyte interface film of the anode. Interface layer, SEI layer) can be stably formed.

Accordingly, the lithium secondary battery including the above-described non-aqueous electrolyte solution minimizes the volume increase of the battery during battery operation, has excellent lifespan characteristics, and has low resistance and improved output characteristics due to excellent lithium ion transfer characteristics.

Hereinafter, the present invention will be described in more detail to aid understanding of the present invention. At this time, the terms or words used in this specification and claims should not be construed as being limited to ordinary or dictionary meanings, and the inventor appropriately defines the concept of terms in order to explain his/her invention in the best way. It should be interpreted as meaning and concept consistent with the technical idea of the present invention based on the principle that it can be done.

Also, in this specification, terms such as "comprise", "include" or "having" are intended to indicate that there is an embodied feature, number, step, component, or combination thereof, but not one or more other It should be understood that it does not preclude the possibility of the presence or addition of features, numbers, steps, components, or combinations thereof.

In the present specification, the average particle diameter (D ₅₀ ) may be defined as a particle diameter corresponding to 50% of the cumulative volume in the particle diameter distribution curve of the particles. The average particle diameter (D ₅₀ ) may be measured using, for example, a laser diffraction method. The laser diffraction method is generally capable of measuring particle diameters of several millimeters in the submicron region, and can obtain results with high reproducibility and high resolution.

Hereinafter, the non-aqueous electrolyte solution of the present invention and a lithium secondary battery including the same will be described in detail.

non-aqueous electrolyte

The present invention provides a non-aqueous electrolyte solution. Specifically, the non-aqueous electrolyte may be a non-aqueous electrolyte for a lithium secondary battery.

Specifically, the non-aqueous electrolyte solution according to the present invention includes a lithium salt; organic solvents; and a compound represented by Formula 1 below.

[Formula 1]

In Formula 1, R ₁ and R ₂ are each independently a substituent selected from an alkyl group having 1 to 10 carbon atoms and an aryl group having 6 to 14 carbon atoms, and R ₃ , R ₄ , R ₅ , and R ₆ are each independently A substituent selected from the group consisting of hydrogen, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, and an aryl group having 6 to 14 carbon atoms, wherein R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ In at least one substituent of, at least one hydrogen is substituted with a halogen element selected from the group consisting of F, Br, Cl and I.

The non-aqueous electrolyte solution according to the present invention includes a lithium salt; organic solvents; And by including the compound represented by Formula 1, it is characterized in that the lithium ion transfer characteristics, electrochemical stability and battery durability can be improved. Specifically, the compound represented by Formula 1 included in the non-aqueous electrolyte according to the present invention has a higher melting point than conventional carbonate-based compounds, has stable electrochemical properties, and does not generate gaseous by-products such as CO ₂ even when decomposed, so that lithium When the secondary battery is driven, it is possible to prevent an increase in the volume of the battery and a decrease in battery durability. In addition, the compound included in the non-aqueous electrolyte according to the present invention can form a coordination structure with lithium ions by including a halogen element such as F, Br, Cl, I, etc. in the compound, thereby improving lithium ion transfer performance, It is possible to increase the energy level of the HOMO (Highest Occupied Molecular Orbital) of the compound, so that oxidation stability can be remarkably improved, by-product formation by decomposition reaction is prevented, and reductive decomposition easily occurs, thereby forming a solid electrolyte interface film of the anode. Interface later, SEI layer) can be stably formed.

Accordingly, the lithium secondary battery including the above-described non-aqueous electrolyte solution minimizes the volume increase of the battery during battery operation, has excellent lifespan characteristics, and has low resistance and improved output characteristics due to excellent lithium ion transfer characteristics.

(1) lithium salt

The non-aqueous electrolyte solution of the present invention contains a lithium salt. The lithium salt is used as an electrolyte salt in a lithium secondary battery and is used as a medium for transferring lithium ions.

Typically, lithium salts are LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiN(C ₂ F ₅ SO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ , CF ₃ SO ₃ Li, LiC(CF ₃ SO ₂ ) ₃ , LiC ₄ BO ₈ , LiTFSI, _LiFSI , and at least one selected from the group consisting of LiClO ₄ . It may include, but is not limited to. Meanwhile, the lithium salt may be used alone or in combination of two or more, if necessary.

The lithium salt may be included in the non-aqueous electrolyte at a concentration of 0.5M to 5M, preferably at a concentration of 0.5M to 4M. When the concentration of the lithium salt is within the above range, the concentration of lithium ions in the non-aqueous electrolyte is appropriate, so that the battery can be properly charged and discharged, and the viscosity of the non-aqueous electrolyte is appropriate, so that wetting within the battery is improved, thereby improving battery performance. It can be.

The lithium salt may be included in the nonaqueous electrolyte in an amount of 5% to 20% by weight, specifically 7% to 15% by weight. When the lithium salt is included in the above range, the concentration of lithium ions in the non-aqueous electrolyte is appropriate, so that the battery can be properly charged and discharged, and the viscosity of the non-aqueous electrolyte is appropriate, so that wetting in the battery is improved, thereby improving battery performance. It can be.

(2) a compound represented by Formula 1

The present invention includes a compound represented by Formula 1 below.

[Formula 1]

In Formula 1, R ₁ and R ₂ are each independently a substituent selected from an alkyl group having 1 to 10 carbon atoms and an aryl group having 6 to 14 carbon atoms, and R ₃ , R ₄ , R ₅ , and R ₆ are each independently A substituent selected from the group consisting of hydrogen, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, and an aryl group having 6 to 14 carbon atoms, wherein R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ In at least one substituent of, at least one hydrogen is substituted with a halogen element selected from the group consisting of F, Br, Cl and I.

In the case of a conventional non-aqueous electrolyte, a carbonate-based compound is generally included, and specifically, a linear carbonate-based compound or a cyclic carbonate-based compound may be used as an organic solvent. At this time, in the case of cyclic carbonate-based compounds, there is a problem of generating gaseous by-products such as CO and CO ₂ due to ring opening during battery operation. These gaseous by-products may cause problems such as an increase in the volume of the lithium secondary battery and a decrease in durability. In addition, since the cyclic carbonate-based compound participates in the formation reaction of the solid electrolyte interface layer (hereinafter referred to as SEI layer) of the negative electrode by reduction decomposition, the oxidation stability of the compound is stable for lithium secondary batteries. It is important for driving and life characteristics.

In this respect, the present invention is characterized in that lithium ion transfer performance, electrochemical stability, and battery durability can be improved by including the compound represented by Formula 1 in the non-aqueous electrolyte. Specifically, the compound represented by Chemical Formula 1 may be partially substituted or substituted for the cyclic carbonate-based compound in a non-aqueous electrolyte, for example. The compound represented by Chemical Formula 1 has a high melting point, has stable electrochemical properties, and does not generate gaseous by-products even when decomposed during battery operation, thereby preventing an increase in the volume of the battery when driving a lithium secondary battery, and greatly improving battery durability. and the lifespan performance of the battery can be significantly improved.

In addition, since the compound represented by Formula 1 contains halogen elements such as F, Br, Cl, and I that enable it to function as an electron withdrawing group in the compound, the oxidation stability of the compound is improved to reduce Decomposition can occur easily, so the SEI layer of the negative electrode can be stably formed, and it can have ion transport performance due to its high dielectric constant. Accordingly, the non-aqueous electrolyte solution of the present invention can significantly improve the output performance, lifespan performance, and battery durability of the lithium secondary battery.

In Formula 1, the halogen element may be selected from the group consisting of F, Br, Cl, and I, and specifically may be F in terms of high electron withdrawing effect and oxidation stability enhancing effect. .

In Formula 1, R ₁ and R ₂ may be each independently a substituent selected from an alkyl group having 1 to 10 carbon atoms and an aryl group having 6 to 14 carbon atoms, and specifically prevents occurrence of steric hinderance in the compound and may be an alkyl group having 1 to 5 carbon atoms independently of each other, and more specifically, a methyl group, in terms of preventing an increase in the viscosity of the non-aqueous electrolyte solution to increase mass transfer performance. On the other hand, when R ₁ and R ₂ are hydrogen, it is not preferable because the stability of the compound is lowered due to the reactivity of hydrogen connected to nitrogen.

In Formula 1, R ₃ , R ₄ , R ₅ , and R ₆ are each independently selected from the group consisting of hydrogen, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, and an aryl group having 6 to 14 carbon atoms. It may be a selected substituent, and specifically, hydrogen, an alkyl group having 1 to 5 carbon atoms, and a carbon number independently of each other in terms of preventing the occurrence of steric hinderance of the compound and preventing the increase in viscosity of the non-aqueous electrolyte to increase the mass transfer performance. It may be a substituent selected from the group consisting of 1 to 5 alkoxy groups, and more specifically, may be substituents independently selected from the group consisting of hydrogen, a methyl group, and a methoxy group.

In one or more substituents of R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ , one or more hydrogens may be substituted with a halogen element selected from the group consisting of F, Br, Cl and I. The R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ One or more halogen elements substituted with one or more substituents (specifically, a halogen element selected from the group consisting of F, Br, Cl and I) are Functioning as an electron withdrawing group in the compound, it can improve the transfer performance of lithium ions and improve the oxidation stability of the compound.

Specifically, in at least one substituent of R ₃ , R ₄ , R ₅ and R ₆ , at least one hydrogen may be substituted with a halogen element selected from the group consisting of F, Br, Cl and I. More specifically, when one or more hydrogens in one or more substituents of R ₃ , R ₄ , R ₅ and R ₆ are substituted with a halogen element selected from the group consisting of F, Br, Cl and I, R ₁ and R ₂ A halogen element selected from the group consisting of F, Br, Cl and I may not be substituted for hydrogen present in . The oxidation stability improvement effect obtained by the substitution or presence of a halogen element in the compound is not limited to the substitution position, but the oxidation stability may be slightly reduced due to the electron donating effect of nitrogen adjacent to R ₁ and R ₂ Considering that it is possible, it is preferable that a halogen element is present or substituted in one or more of R ₃ , R ₄ , R ₅ and R ₆ .

More specifically, in one substituent of R ₃ , R ₄ , R ₅ and R ₆ , one or more hydrogens may be substituted with a halogen element selected from the group consisting of F, Br, Cl and I. For example, one or more hydrogen present in R ₃ may be substituted with a halogen element selected from the group consisting of F, Br, Cl and I, and hydrogen present in R ₄ , R ₅ and R ₆ may be replaced by F, Br , a halogen element selected from the group consisting of Cl and I may be unsubstituted. Considering the compatibility of preventing an increase in the viscosity of the non-aqueous electrolyte solution and a decrease in the lithium ion transport performance due to an increase in the number of substituents, and improving the oxidation stability of the compound and improving the durability of the battery, among R ₃ , R ₄ , R ₅ and R ₆ In one substituent, it is preferable that at least one hydrogen is substituted with a halogen element selected from the group consisting of F, Br, Cl and I.

More specifically, one or more substituents of R ₃ , R ₄ , R ₅ and R ₆ may be independently selected from a trifluoromethyl group (-CF ₃ ) and a trifluoromethoxy group (-OCF ₃ ). Preferably, the substituent of one of R ₃ , R ₄ , R ₅ and R ₆ may be selected from a trifluoromethyl group and a trifluoromethoxy group. When the substituent is used, the above-described effects of improving lithium ion transfer performance, battery durability, and oxidation stability can be better realized.

More specifically, at least one substituent selected from R ₃ , R ₄ , R ₅ and R ₆ may independently be a trifluoromethoxy group. Preferably, one substituent of R ₃ , R ₄ , R ₅ and R ₆ may be a trifluoromethoxy group. In the case of the substituent, additional improvement in lithium ion transfer performance can be expected due to the oxygen present in the trifluoromethoxy group.

The compound represented by Formula 1 may include at least one selected from a compound represented by Formula 2 below and a compound represented by Formula 3 below, and may specifically include a compound represented by Formula 3 below.

[Formula 2]

[Formula 3]

In Formula 2 and Formula 3, R ₁ and R ₂ may be as described in Formula 1 above. Specifically, in Formula 2 and Formula 3, R ₁ and R ₂ may each independently be a substituent selected from an alkyl group having 1 to 10 carbon atoms and an aryl group having 6 to 14 carbon atoms, and specifically, independently of each other, a compound It may be an alkyl group having 1 to 5 carbon atoms, and more specifically, a methyl group, in terms of preventing occurrence of steric hinderance and increasing mass transfer performance by preventing an increase in the viscosity of the non-aqueous electrolyte.

Specifically, the compound represented by Chemical Formula 1 may include at least one selected from a compound represented by Chemical Formula 4 and a compound represented by Chemical Formula 5 below.

[Formula 4]

[Formula 5]

The compound represented by Formula 1 may be included in the non-aqueous electrolyte in an amount of 0.2% to 45% by weight, specifically 5% to 30% by weight. When the compound is included in the above range, the lithium ion transport performance of the non-aqueous electrolyte solution can be further improved, the stable formation of the SEI layer is possible, and the ion conductivity is lowered due to excessively high viscosity of the electrolyte, and the wettability of the electrolyte is improved. problems can be prevented.

(3) organic solvent

The non-aqueous electrolyte solution according to the present invention contains an organic solvent. The organic solvent is a non-aqueous solvent commonly used in lithium secondary batteries, and is not particularly limited as long as decomposition due to an oxidation reaction or the like can be minimized during charging and discharging of the secondary battery.

Specifically, the organic solvent may include at least one selected from linear carbonate, cyclic carbonate, linear ester, cyclic ester, ether, glyme, and nitrile. The organic solvent may preferably include at least one selected from linear carbonates and cyclic carbonates, and more preferably include linear carbonates and cyclic carbonates. In particular, existing non-aqueous electrolytes can generally use cyclic carbonate as an organic solvent for high permittivity and dissociation of lithium salts. can do. In particular, since the compound represented by Formula 1 has high oxidation stability, excellent lithium ion transport performance, and does not generate gaseous by-products, it can improve durability and lifespan characteristics of a lithium secondary battery, so when cyclic carbonate is used Compared to the above, excellent battery characteristics can be exhibited at a desirable level.

The linear carbonate is at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl carbonate (EMC), methylpropyl carbonate and ethylpropyl carbonate can include

The cyclic carbonate is ethylene carbonate (ethylene carbonate, EC), propylene carbonate (propylene carbonate, PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3 - It may include at least one selected from the group consisting of pentylene carbonate, vinylene carbonate and fluoroethylene carbonate (FEC).

Specific examples of the linear ester include methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate, but are not limited thereto.

Specific examples of the cyclic ester include γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone, but are not limited thereto.

Specific examples of the ether include dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether, ethyl propyl ether, 1,3-dioxolane (DOL) and 2,2-bis (trifluoromethyl ) -1,3-dioxolane (TFDOL) and the like, but are not limited thereto.

Specific examples of the glyme include dimethoxyethane (glyme, DME), diethoxyethane, diglyme, tri-glyme, and tetra-glyme (TEGDME), but are limited thereto. It is not.

Specific examples of the nitrile include acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, 2-fluorobenzonitrile, 4-fluorobenzo nitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, 4-fluorophenylacetonitrile, etc., but are not limited thereto.

Specifically, the organic solvent may include linear carbonate. Existing non-aqueous electrolytes can generally use cyclic carbonate together with linear carbonate for high permittivity and dissociation of lithium salts. can In particular, since the compound represented by Formula 1 has high oxidation stability, excellent lithium ion transport performance, and does not generate gaseous by-products, it can improve durability and lifespan characteristics of a lithium secondary battery, so when cyclic carbonate is used Compared to the above, excellent battery characteristics can be exhibited at a desirable level. More specifically, the organic solvent may consist of linear carbonate.

The organic solvent may be included in the non-aqueous electrolyte in an amount of 48% to 90% by weight, specifically 55% to 80% by weight.

(4) Additives

The non-aqueous electrolyte solution may further include an additive.

Specifically, the non-aqueous electrolyte solution includes vinylene carbonate, vinyl ethylene carbonate, propane sultone, succinonitrile, adiponitrile, ethylene sulfate ), Propene Sultone, fluoroethylene carbonate, LiPO ₂ F ₂ , LiODFB (Lithium difluorooxalatoborate), LiBOB (Lithium bis-(oxalato)borate), TMSPa (3-trimethoxysilanyl-propyl- N-aniline), TMSPi (Tris (trimethylsilyl) Phosphite), and LiBF ₄ - may further include at least one additive selected from the group consisting of, specifically, an additive containing vinylene carbonate. . When the additive is included in the non-aqueous electrolyte, it is preferable in that it forms a stable solid electrolyte interface film (SEI layer) on the negative electrode, suppresses additional decomposition of the electrolyte, and improves lifespan characteristics.

The additive may be included in the nonaqueous electrolyte in an amount of 0.1% to 15% by weight, preferably 0.3% to 5% by weight.

lithium secondary battery

In addition, the present invention provides a lithium secondary battery including the above-described non-aqueous electrolyte.

Specifically, the lithium secondary battery according to the present invention includes a negative electrode; an anode facing the cathode; a separator facing the cathode and the anode; and the aforementioned non-aqueous electrolyte.

At this time, the lithium secondary battery of the present invention can be manufactured according to a conventional method known in the art. For example, after forming an electrode assembly by sequentially stacking a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode, the electrode assembly is inserted into the battery case, and the non-aqueous electrolyte according to the present invention is injected. .

The negative electrode may include a negative electrode current collector; and an anode active material layer disposed on at least one surface of the anode current collector.

The anode current collector is not particularly limited as long as it does not cause chemical change in the battery and has high conductivity. Specifically, the negative electrode current collector may be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like, aluminum-cadmium alloy, or the like. there is.

The negative current collector may typically have a thickness of 3 to 500 μm.

The negative electrode current collector may form fine irregularities on the surface to enhance bonding strength of the negative electrode active material. For example, the negative current collector may be used in various forms such as a film, sheet, foil, net, porous material, foam, or non-woven fabric.

The anode active material layer is disposed on at least one surface of the anode current collector. Specifically, the negative electrode active material layer may be disposed on one side or both sides of the negative electrode current collector.

The anode active material layer may include an anode active material.

The anode active material is a material capable of reversibly intercalating/deintercalating lithium ions, and may include at least one selected from the group consisting of a carbon-based active material, a (semi-)metal-based active material, and a lithium metal. Specifically, the carbon-based active material And (semi) may include at least one selected from metal-based active material.

The carbon-based active material may include at least one selected from the group consisting of artificial graphite, natural graphite, hard carbon, soft carbon, carbon black, graphene, and fibrous carbon, and preferably composed of artificial graphite and natural graphite. It may contain at least one selected from the group.

The average particle diameter (D ₅₀ ) of the carbon-based active material may be 10 μm to 30 μm, preferably 15 μm to 25 μm, in terms of structural stability during charging and discharging and reducing side reactions with the electrolyte.

Specifically, the (semi-)metal-based active material is Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, at least one (semi)metal selected from the group consisting of V, Ti, and Sn; In the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, V, Ti, and Sn an alloy of at least one selected (semi)metal and lithium; In the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, V, Ti, and Sn an oxide of at least one selected (semi)metal; lithium titanium oxide (LTO); lithium vanadium oxide; etc. may be included.

More specifically, the (semi)metal-based active material may include a silicon-based active material.

The silicon-based active material may include a compound represented by SiO _x (0≤x<2). Since SiO ₂ does not react with lithium ions and cannot store lithium, x is preferably within the above range, and more preferably, the silicon-based oxide may be SiO.

The average particle diameter (D ₅₀ ) of the silicon-based active material may be 1 μm to 30 μm, preferably 2 μm to 15 μm, in terms of reducing side reactions with the electrolyte solution while maintaining structural stability during charging and discharging.

The negative active material may be included in the negative active material layer in an amount of 60% to 99% by weight, preferably 75% to 95% by weight.

The negative active material layer may further include a binder and/or a conductive material together with the negative active material.

The binder is used to improve battery performance by improving adhesion between the negative electrode active material layer and the negative electrode current collector, and is, for example, polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co- HFP), polyvinylidenefluoride (PVDF), polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regeneration Cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, and hydrogen thereof may include at least one selected from the group consisting of materials substituted with Li, Na or Ca, and may also include various copolymers thereof.

The binder may be included in the negative electrode active material layer in an amount of 0.5% to 10% by weight, preferably 1% to 5% by weight.

The conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery, and examples include graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, ketjen black, channel black, farnes black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes; fluorocarbons; metal powders such as aluminum and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.

The conductive material may be included in the negative electrode active material layer in an amount of 0.5% to 10% by weight, preferably 1% to 5% by weight.

The negative electrode active material layer may have a thickness of 10 μm to 100 μm, preferably 50 μm to 80 μm.

The anode may be manufactured by coating at least one surface of the anode current collector with an anode slurry containing an anode active material, a binder, a conductive material, and/or a solvent for forming the anode slurry, followed by drying and rolling.

The solvent for forming the negative electrode slurry is, for example, distilled water, NMP (N-methyl-2-pyrrolidone), ethanol, methanol, and isopropyl alcohol in terms of facilitating dispersion of the negative electrode active material, binder and / or conductive material It may include at least one selected from the group, preferably distilled water. The solid content of the negative electrode slurry may be 30 wt% to 80 wt%, specifically 40 wt% to 70 wt%.

The anode faces the cathode.

The positive electrode may include a positive electrode current collector; and a cathode active material layer disposed on at least one surface of the cathode current collector.

The positive current collector is not particularly limited as long as it does not cause chemical change in the battery and has high conductivity. Specifically, the cathode current collector may include at least one selected from the group consisting of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, and an aluminum-cadmium alloy, preferably aluminum.

The thickness of the cathode current collector may typically have a thickness of 3 to 500 μm.

The positive electrode current collector may form fine irregularities on the surface to enhance bonding strength of the negative electrode active material. For example, the cathode current collector may be used in various forms such as a film, sheet, foil, net, porous material, foam, or non-woven fabric.

The positive electrode active material layer is disposed on at least one surface of the positive electrode current collector. Specifically, the positive electrode active material layer may be disposed on one side or both sides of the positive electrode current collector.

The cathode active material layer may include a cathode active material.

The cathode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, a lithium transition metal composite oxide containing lithium and at least one transition metal composed of nickel, cobalt, manganese, and aluminum, Preferably, a transition metal including nickel, cobalt, and manganese and a lithium transition metal composite oxide including lithium may be included.

For example, the lithium transition metal composite oxide includes lithium-manganese-based oxide (eg, LiMnO ₂ , LiMn ₂ O ₄ , etc.), lithium-cobalt-based oxide (eg, LiCoO ₂ , etc.), lithium-nickel based oxides (eg, LiNiO ₂ , etc.), lithium-nickel-manganese based oxides (eg, LiNi _1-Y Mn _Y O ₂ (where 0<Y<1), LiMn _2-z Ni _z O ₄ (here, 0<Z<2), etc.), lithium-nickel-cobalt-based oxide (eg, LiNi _1-Y1 Co _Y1 O ₂ (here, 0<Y1<1), etc.), lithium-manganese -Cobalt-based oxides (eg, LiCo _1-Y2 Mn _Y2 O ₂ (where 0<Y2<1), LiMn _2-z1 Co _z1 O ₄ (where 0<Z1<2), etc.), lithium -Nickel-manganese-cobalt-based oxide (eg, Li(Ni _p Co _q Mn _r1 ) O ₂ (here, 0<p<1, 0<q<1, 0<r1<1, p+q+ r1=1) or Li(Ni _p1 Co _q1 Mn _r2 )O ₄ (where 0<p1<2, 0<q1<2, 0<r2<2, p1+q1+r2=2), etc.), or Lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni _p2 Co _q2 Mn _r3 M _S2 )O ₂ where M is Al, Fe, V, Cr, Ti, Ta, Mg and It is selected from the group consisting of Mo, and p2, q2, r3 and s2 are atomic fractions of independent elements, respectively, 0 <p2 <1, 0 <q2 <1, 0 <r3 <1, 0 <s2 <1, p2 +q2+r3+s2=1), etc.), and any one or two or more of these compounds may be included. Among them, in that the capacity characteristics and stability of the battery can be improved, the lithium transition metal composite oxide is LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , lithium nickel-manganese-cobalt oxide (eg, Li(Ni _0.6 Mn _0.2 Co _0.2 )O ₂ , Li(Ni _0.5 Mn _0.3 Co _0.2 )O ₂ , Li(Ni _0.7 Mn _0.15 Co _0.15 )O ₂ or Li(Ni _0.8 Mn _0.1 Co _0.1 )O ₂ , etc.), or lithium nickel cobalt aluminum oxide (eg For example, it may be Li (Ni _0.8 Co _0.15 Al _0.05 ) O ₂ , etc.), and considering the remarkable effect of improving the type and content ratio control of the constituent elements forming the lithium transition metal composite oxide, the lithium transition metal Complex oxides are Li(Ni _0.6 Mn _0.2 Co _0.2 )O ₂ , Li(Ni _0.5 Mn _0.3 Co _0.2 )O ₂ , Li(Ni _0.7 Mn _0.15 Co _0.15 )O ₂ or Li(Ni _0.8 Mn _0.1 Co _0.1 )O ₂ And the like, any one or a mixture of two or more of them may be used.

More specifically, the cathode active material is a lithium transition metal composite oxide, and may contain 60 mol% or more of nickel based on the total number of moles of transition metals included in the lithium transition metal composite oxide. Specifically, the cathode active material is a lithium transition metal composite oxide, the transition metal is nickel; and at least one selected from manganese, cobalt, and aluminum, and may include nickel in an amount of 60 mol% or more, specifically, 60 mol% to 90 mol%, based on the total number of moles of the transition metal. When such a lithium transition metal composite oxide using a high nickel content is used together with the above-described non-aqueous electrolyte, it is preferable in terms of reducing by-products in the gas phase generated by structural collapse.

The positive electrode active material may be included in an amount of 80% to 99% by weight, preferably 92% to 98.5% by weight in the positive electrode active material layer in consideration of exhibiting sufficient capacity of the positive electrode active material.

The positive electrode active material layer may further include a binder and/or a conductive material together with the positive electrode active material.

The binder is a component that assists in the binding of the active material and the conductive material and the binding to the current collector, specifically polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose in the group consisting of woods, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber and fluororubber It may contain at least one selected species, preferably polyvinylidene fluoride.

The binder may be included in an amount of 1% to 20% by weight, preferably 1.2% to 10% by weight, in the positive electrode active material layer in order to sufficiently secure binding force between components such as the positive electrode active material.

The conductive material may be used to assist and improve the conductivity of a secondary battery, and is not particularly limited as long as it has conductivity without causing chemical change. Specifically, the cathode conductive material is graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, ketjen black, channel black, farnes black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes; fluorocarbons; metal powders such as aluminum and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; And it may include at least one selected from the group consisting of polyphenylene derivatives, and may preferably include carbon black in terms of improving conductivity.

The conductive material may be included in an amount of 1 wt % to 20 wt %, preferably 1.2 wt % to 10 wt %, in the cathode active material layer in order to sufficiently secure electrical conductivity.

The thickness of the cathode active material layer may be 30 μm to 400 μm, preferably 40 μm to 110 μm.

The positive electrode may be prepared by coating a positive electrode slurry including a positive electrode active material and optionally a binder, a conductive material, and a solvent for forming the positive electrode slurry on the positive electrode current collector, followed by drying and rolling.

The solvent for forming the positive electrode slurry may include an organic solvent such as N-methyl-2-pyrrolidone (NMP). The solid content of the positive electrode slurry may be 40 wt% to 90 wt%, specifically 50 wt% to 80 wt%.

The separator is interposed between the anode and the cathode.

The separator separates the negative electrode and the positive electrode and provides a passage for lithium ion movement, and can be used without particular limitation as long as it is normally used as a separator in a lithium secondary battery. Excellent is desirable. Specifically, a porous polymer film, for example, a porous polymer film made of polyolefin-based polymers such as ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, and ethylene/methacrylate copolymer, or these A laminated structure of two or more layers of may be used. In addition, conventional porous non-woven fabrics, for example, non-woven fabrics made of high-melting glass fibers, polyethylene terephthalate fibers, and the like may be used. In addition, a coated separator containing a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength, and may be selectively used in a single-layer or multi-layer structure.

The external shape of the lithium secondary battery of the present invention is not particularly limited, and may be, for example, a cylindrical shape, a prismatic shape, a pouch shape, or a coin shape.

The lithium secondary battery according to the present invention may be used as a battery cell used as a power source for a small device or may be used as a unit cell of a medium or large battery module including a plurality of battery cells.

The lithium secondary battery according to the present invention can be usefully used in the field of portable devices such as mobile phones, notebook computers, and digital cameras, and fields of electric vehicles such as hybrid electric vehicles (HEVs) and electric vehicles (EVs). can

In addition, the present invention provides a battery module including the lithium secondary battery as a unit cell, and a battery pack including the battery module.

The battery module or battery pack may include a power tool; electric vehicle; hybrid electric vehicle; and a power storage system.

Hereinafter, the present invention will be described in more detail through specific examples. However, the following examples are only examples to help understanding of the present invention, and do not limit the scope of the present invention. It is obvious to those skilled in the art that various changes and modifications are possible within the scope and spirit of the present disclosure, and it is natural that such changes and modifications fall within the scope of the appended claims.

Example

Example 1: Preparation of non-aqueous electrolyte solution

A mixture of LiPF ₆ as a lithium salt, ethylene carbonate (EC) and ethylmethyl carbonate (EMC) as an organic solvent in a weight ratio of 31.0:55.9 (volume ratio of about 30:70), a compound represented by the following formula (4), and additives A non-aqueous electrolyte solution was prepared by mixing vinylene carbonate as .

[Formula 4]

The lithium salt was contained in the non-aqueous electrolyte at a concentration of 1M (12.0% by weight in the non-aqueous electrolyte).

The vinylene carbonate was included in the non-aqueous electrolyte in an amount of 0.5% by weight.

The compound represented by Chemical Formula 4 was included in 0.5% by weight in the non-aqueous electrolyte solution, and the organic solvent was included in 87.0% by weight in the non-aqueous electrolyte solution.

Example 2: Preparation of non-aqueous electrolyte solution

A mixture of LiPF ₆ as a lithium salt, ethylene carbonate (EC) and ethylmethyl carbonate (EMC) as organic solvents in a weight ratio of 30.1:54.3 (volume ratio of about 30:70), a compound represented by Formula 4, and additives A non-aqueous electrolyte solution was prepared by mixing vinylene carbonate as .

The lithium salt was contained in the non-aqueous electrolyte at a concentration of 1 M (12.1% by weight in the non-aqueous electrolyte).

The vinylene carbonate was included in the non-aqueous electrolyte in an amount of 0.5% by weight.

The compound represented by Chemical Formula 4 was included in 3.0% by weight of the non-aqueous electrolyte solution, and the organic solvent was included in 84.4% by weight of the non-aqueous electrolyte solution.

Example 3: Preparation of non-aqueous electrolyte solution

A non-aqueous electrolyte solution was prepared in the same manner as in Example 1, except that the compound represented by Formula 5 was used instead of the compound represented by Formula 4.

[Formula 5]

Example 4: Preparation of non-aqueous electrolyte solution

A non-aqueous electrolyte solution was prepared in the same manner as in Example 2, except that the compound represented by Formula 5 was used instead of the compound represented by Formula 4.

Example 5: Preparation of non-aqueous electrolyte solution

A non-aqueous electrolyte was prepared by mixing LiPF ₆ as a lithium salt, ethylmethyl carbonate (EMC) as an organic solvent, the compound represented by Chemical Formula 4, and vinylene carbonate as an additive.

The lithium salt was contained in 1 M in the non-aqueous electrolyte solution (included in 13.0% by weight in the non-aqueous electrolyte solution).

The vinylene carbonate was included in the non-aqueous electrolyte in an amount of 0.5% by weight.

The compound represented by Chemical Formula 4 was included in 25.8% by weight of the non-aqueous electrolyte solution, and the organic solvent was included in 60.7% by weight of the non-aqueous electrolyte solution.

Example 6: Preparation of non-aqueous electrolyte solution

A mixture of LiPF ₆ as a lithium salt, ethylene carbonate (EC) and ethylmethyl carbonate (EMC) as organic solvents in a weight ratio of 21.3:57.7 (volume ratio of about 20:70), a compound represented by Formula 4, and additives A non-aqueous electrolyte solution was prepared by mixing vinylene carbonate as .

The lithium salt was contained in 1 M in the non-aqueous electrolyte solution (included in 12.3% by weight in the non-aqueous electrolyte solution).

The vinylene carbonate was included in the non-aqueous electrolyte in an amount of 0.5% by weight.

The compound represented by Chemical Formula 4 was included in the non-aqueous electrolyte at 8.2% by weight, and the organic solvent was included in the non-aqueous electrolyte at 79.0% by weight.

Example 7: Preparation of non-aqueous electrolyte solution

A non-aqueous electrolyte was prepared by mixing LiPF ₆ as a lithium salt, ethylmethyl carbonate (EMC) as an organic solvent, the compound represented by Chemical Formula 5, and vinylene carbonate as an additive.

The lithium salt was contained in 1 M in the non-aqueous electrolyte solution (included in 13.1% by weight in the non-aqueous electrolyte solution).

The vinylene carbonate was included in the non-aqueous electrolyte in an amount of 0.5% by weight.

The compound represented by Chemical Formula 5 was included in the non-aqueous electrolyte at 25.4% by weight, and the organic solvent was included in the non-aqueous electrolyte at 61.1% by weight.

Example 8: Preparation of non-aqueous electrolyte solution

A mixture of LiPF ₆ as a lithium salt, ethylene carbonate (EC) and ethylmethyl carbonate (EMC) as an organic solvent at a weight ratio of 21.4:57.8 (volume ratio of about 20:70), a compound represented by Formula 5, and additives A non-aqueous electrolyte solution was prepared by mixing vinylene carbonate as .

The lithium salt was contained in 1 M in the non-aqueous electrolyte solution (included in 12.4% by weight in the non-aqueous electrolyte solution).

The vinylene carbonate was included in the non-aqueous electrolyte in an amount of 0.5% by weight.

The compound represented by Chemical Formula 5 was included in the non-aqueous electrolyte at 8.0% by weight, and the organic solvent was included in the non-aqueous electrolyte at 79.1% by weight.

Example 9: Preparation of non-aqueous electrolyte solution

A non-aqueous electrolyte was prepared by mixing LiPF ₆ as a lithium salt, ethylmethyl carbonate (EMC) as an organic solvent, the compound represented by Chemical Formula 4, and vinylene carbonate as an additive.

The lithium salt was contained in 1 M in the non-aqueous electrolyte solution (included in 13.0% by weight in the non-aqueous electrolyte solution).

The vinylene carbonate was included in the non-aqueous electrolyte in an amount of 0.5% by weight.

The compound represented by Chemical Formula 4 was included in 34.4% by weight of the non-aqueous electrolyte solution, and the organic solvent was included in 52.1% by weight of the non-aqueous electrolyte solution.

Example 10: Preparation of non-aqueous electrolyte solution

A non-aqueous electrolyte was prepared by mixing LiPF ₆ as a lithium salt, ethylmethyl carbonate (EMC) as an organic solvent, the compound represented by Chemical Formula 5, and vinylene carbonate as an additive.

The lithium salt was contained in 1 M in the non-aqueous electrolyte solution (included in 13.1% by weight in the non-aqueous electrolyte solution).

The vinylene carbonate was included in the non-aqueous electrolyte in an amount of 0.5% by weight.

The compound represented by Chemical Formula 5 was included in the non-aqueous electrolyte at 34.0% by weight, and the organic solvent was included at 52.5% by weight in the non-aqueous electrolyte.

Comparative Example 1: Preparation of non-aqueous electrolyte solution

A mixture of LiPF ₆ as a lithium salt, ethylene carbonate (EC) and ethylmethyl carbonate (EMC) as an organic solvent at a weight ratio of 31.2:56.3 (volume ratio of about 30:70), and vinylene carbonate as an additive to obtain a non-aqueous mixture An electrolyte solution was prepared.

The lithium salt was contained in 1 M in the non-aqueous electrolyte solution (included in 12.0% by weight in the non-aqueous electrolyte solution).

The vinylene carbonate was included in the non-aqueous electrolyte in an amount of 0.5% by weight.

The organic solvent was included in 87.5% by weight of the non-aqueous electrolyte.

Comparative Example 2: Preparation of non-aqueous electrolyte solution

A non-aqueous electrolyte solution was prepared in the same manner as in Example 1, except that the compound represented by the following Chemical Formula 6 was used instead of the compound represented by the Chemical Formula 4.

[Formula 6]

Comparative Example 3: Preparation of non-aqueous electrolyte solution

A non-aqueous electrolyte was prepared in the same manner as in Example 2, except that the compound represented by Chemical Formula 6 was used instead of the compound represented by Chemical Formula 4.

Comparative Example 4: Preparation of non-aqueous electrolyte solution

A non-aqueous electrolyte solution was prepared in the same manner as in Example 1, except that the compound represented by Formula 7 was used instead of the compound represented by Formula 4.

[Formula 7]

Comparative Example 5: Preparation of non-aqueous electrolyte solution

A non-aqueous electrolyte solution was prepared in the same manner as in Example 2, except that the compound represented by Formula 7 was used instead of the compound represented by Formula 4.

Comparative Example 6: Preparation of non-aqueous electrolyte solution

A non-aqueous electrolyte was prepared by mixing LiPF ₆ as a lithium salt, ethylmethyl carbonate (EMC) as an organic solvent, the compound represented by Chemical Formula 6, and vinylene carbonate as an additive.

The lithium salt was contained in 1 M in the non-aqueous electrolyte solution (included in 12.9% by weight in the non-aqueous electrolyte solution).

The vinylene carbonate was included in the non-aqueous electrolyte in an amount of 0.5% by weight.

The compound represented by Chemical Formula 6 was included in 26.5% by weight of the non-aqueous electrolyte solution, and the organic solvent was included in 60.1% by weight of the non-aqueous electrolyte solution.

Comparative Example 7: Preparation of non-aqueous electrolyte solution

A mixture of LiPF ₆ as a lithium salt, ethylene carbonate (EC) and ethylmethyl carbonate (EMC) as an organic solvent in a weight ratio of 21.3:57.5 (volume ratio of about 20:70), a compound represented by Formula 6, and additives A non-aqueous electrolyte solution was prepared by mixing vinylene carbonate as .

The lithium salt was contained in 1 M in the non-aqueous electrolyte solution (included in 12.3% by weight in the non-aqueous electrolyte solution).

The vinylene carbonate was included in the non-aqueous electrolyte in an amount of 0.5% by weight.

The compound represented by Chemical Formula 6 was included in 8.5% by weight of the non-aqueous electrolyte solution, and the organic solvent was included in 78.8% by weight of the non-aqueous electrolyte solution.

Comparative Example 8: Preparation of non-aqueous electrolyte solution

A non-aqueous electrolyte was prepared by mixing LiPF ₆ as a lithium salt, ethylmethyl carbonate (EMC) as an organic solvent, the compound represented by Chemical Formula 7, and vinylene carbonate as an additive.

The lithium salt was contained in 1 M in the non-aqueous electrolyte solution (included in 12.9% by weight in the non-aqueous electrolyte solution).

The vinylene carbonate was included in the non-aqueous electrolyte in an amount of 0.5% by weight.

The compound represented by Chemical Formula 7 was included in 26.2% by weight of the non-aqueous electrolyte solution, and the organic solvent was included in 60.4% by weight of the non-aqueous electrolyte solution.

Comparative Example 9: Preparation of non-aqueous electrolyte solution

A mixture of LiPF ₆ as a lithium salt, ethylene carbonate (EC) and ethylmethyl carbonate (EMC) as organic solvents in a weight ratio of 21.3:57.6 (volume ratio of about 20:70), a compound represented by Formula 7, and additives A non-aqueous electrolyte solution was prepared by mixing vinylene carbonate as .

The lithium salt was contained in 1 M in the non-aqueous electrolyte solution (included in 12.3% by weight in the non-aqueous electrolyte solution).

The vinylene carbonate was included in the non-aqueous electrolyte in an amount of 0.5% by weight.

The compound represented by Chemical Formula 7 was included in the non-aqueous electrolyte at 8.3% by weight, and the organic solvent was included in the non-aqueous electrolyte at 78.9% by weight.

non-aqueous electrolyte Lithium salt (LiPF ₆ ) organic solvent imidazolinone compound vinylene carbonate Weight % (based on non-aqueous electrolyte) Kinds Weight % (based on non-aqueous electrolyte) Kinds Weight % (based on non-aqueous electrolyte) Weight % (based on non-aqueous electrolyte) Example 1 12.0 EC and EMC (volume ratio approx. 30:70) 87.0 formula 4 0.5 0.5 Example 2 12.1 EC and EMC (volume ratio approx. 30:70) 84.4 formula 4 3.0 0.5 Example 3 12.0 EC and EMC (volume ratio approx. 30:70) 87.0 Formula 5 0.5 0.5 Example 4 12.1 EC and EMC (volume ratio approx. 30:70) 84.4 Formula 5 3.0 0.5 Example 5 13.0 EMC 60.7 formula 4 25.8 0.5 Example 6 12.3 EC and EMC (volume ratio approx. 20:70) 79.0 formula 4 8.2 0.5 Example 7 13.1 EMC 61.1 Formula 5 25.4 0.5 Example 8 12.4 EC and EMC (volume ratio approx. 20:70) 79.1 Formula 5 8.0 0.5 Example 9 13.0 EMC 52.1 formula 4 34.4 0.5 Example 10 13.1 EMC 52.5 Formula 5 34.0 0.5 Comparative Example 1 12.0 EC and EMC (volume ratio approx. 30:70) 87.5 - - 0.5 Comparative Example 2 12.0 EC and EMC (volume ratio approx. 30:70) 87.0 formula 6 0.5 0.5 Comparative Example 3 12.1 EC and EMC (volume ratio approx. 30:70) 84.4 formula 6 3.0 0.5 Comparative Example 4 12.0 EC and EMC (volume ratio approx. 30:70) 87.0 Formula 7 0.5 0.5 Comparative Example 5 12.1 EC and EMC (volume ratio approx. 30:70) 84.4 Formula 7 3.0 0.5 Comparative Example 6 12.9 EMC 60.1 formula 6 26.5 0.5 Comparative Example 7 12.3 EC and EMC (volume ratio approx. 20:70) 78.8 formula 6 8.5 0.5 Comparative Example 8 12.9 EMC 60.4 Formula 7 26.2 0.5 Comparative Example 9 12.3 EC and EMC (volume ratio approx. 20:70) 78.9 Formula 7 8.3 0.5

Experimental example

<Manufacture of secondary battery>

1. Preparation of cathode

Artificial graphite as an anode active material, carbon black as a conductive material (product name: Super C65, manufacturer: Timcal), an acrylic binder (BM-L302, manufactured by Zeon) as a binder, and carboxymethylcellulose as a thickener in a ratio of 95:1.5:2.3:1.2 A negative electrode slurry was prepared by adding distilled water as a solvent for forming the negative electrode slurry at a weight ratio of .

As a negative electrode current collector, the negative electrode slurry was coated with a loading amount of 350 mg / 25 cm ² on one surface of a copper current collector, rolled, and dried in a vacuum oven at 130 ° C. for 10 hours to form a negative electrode active material layer, This was used as a cathode.

2. Manufacture of anode

Li[Ni _0.86 Co _0.05 Mn _0.07 Al _0.02 ]O ₂ as a cathode active material, carbon black (product name: Super C65, manufacturer: Timcal) as a conductive material, and polyvinylidene fluoride (PVdF) as a binder in a ratio of 97.5:1.5:1.0. A positive electrode slurry was prepared by adding N-methyl-2-pyrrolidone (NMP) as a solvent for forming a positive electrode slurry in a weight ratio.

As a positive electrode current collector, the positive electrode slurry was coated with a loading amount of 607 mg/25 cm ² on one surface of an aluminum current collector, rolled, and dried in a vacuum oven at 130 ° C. for 10 hours to form a positive electrode active material layer, This was made the positive electrode.

3. Manufacturing of lithium secondary battery

A lithium secondary battery of Example 1 was prepared by injecting the non-aqueous electrolyte solution prepared in Example 1 after interposing a porous separator between the prepared positive electrode and the negative electrode in the battery case.

Examples 2 to 10 and Comparison were performed in the same manner as in the manufacturing method of the lithium secondary battery of Example 1, except that the nonaqueous electrolyte of Examples 2 to 10 and Comparative Examples 1 to 9 was used instead of the nonaqueous electrolyte of Example 1. Lithium secondary batteries of Examples 1 to 9 were manufactured, respectively.

Experimental Example 1: Evaluation of high temperature cycle capacity retention rate

Using the lithium secondary batteries of Examples 1 to 10 and Comparative Examples 1 to 9, high-temperature cycle capacity retention rates were evaluated.

Specifically, the lithium secondary batteries of Examples 1 to 10 and Comparative Examples 1 to 9 were charged up to 4.2V under CC/CV, 0.33C conditions at 45° C. using an electrochemical charger and discharger, and then under CC, 0.33C conditions. 200 cycles of charging and discharging were performed with discharging to 3 V as one cycle, and the capacity retention rate was measured.

The capacity retention rate was calculated by the formula below, and the results are shown in Table 2 below.

Capacity retention rate (%) = (discharge capacity after 200 cycles/discharge capacity after 1 cycle) × 100

Experimental Example 2: Evaluation of initial resistance and resistance increase rate

The lithium secondary batteries of Examples 1 to 10 and Comparative Examples 1 to 9 were charged to 4.2V under CC/CV, 0.33C conditions at 45° C., and then discharged to 3V under CC, 0.33C conditions, 200 cycles as one cycle. Charging/discharging was performed.

After one cycle of charging and discharging, the discharge capacity after one cycle is measured using an electrochemical charger and discharger, the SOC is adjusted to 50% of the SOC, and a pulse of 2.5C is applied for 10 seconds, and the voltage before the pulse is applied And, the initial resistance was calculated through the difference in voltage after application.

After 200 cycles of charging and discharging, the resistance after 200 cycles was calculated in the same manner as above, and the resistance increase rate was calculated using the equation below, and the results are shown in Table 2 below.

Resistance increase rate (%) = (resistance after 200 cycles - initial resistance)/initial resistance × 100

Experimental Example 3: Volume increase rate

The lithium secondary batteries of Examples 1 to 10 and Comparative Examples 1 to 9 were charged and discharged for 200 cycles in the same manner as in Experimental Example 1. At this time, the volume of the lithium secondary battery before charging and discharging (initial volume) and the volume of the lithium secondary battery after 200 cycles were measured, and the volume increase rate was calculated by the following formula, and the results are shown in Table 2 below.

Volume increase rate (%) = (volume of lithium secondary battery after 200 cycles - initial volume) / initial volume × 100

Experimental Example 1 Experimental Example 2 Experimental Example 3 Capacity retention rate (%) Initial Resistance (mOhm) Resistance increase rate (%) Volume increase rate (%) Example 1 92.4 8.54 5.5 23.4 Example 2 93.5 8.97 5.1 21.0 Example 3 95.7 7.45 3.5 18.4 Example 4 96.3 7.56 3.2 15.7 Example 5 97.3 3.45 2.6 5.4 Example 6 96.7 4.25 3.1 6.9 Example 7 98.8 2.47 1.1 3.4 Example 8 98.3 3.10 1.4 4.1 Example 9 91.2 6.23 10.6 12.3 Example 10 92.3 5.95 9.7 10.4 Comparative Example 1 85.3 12.51 15.6 59.7 Comparative Example 2 87.7 11.54 13.4 51.3 Comparative Example 3 88.5 11.98 13.1 50.4 Comparative Example 4 87.2 12.13 12.8 48.7 Comparative Example 5 88.1 12.55 12.1 47.1 Comparative Example 6 78.2 9.45 35.6 40.3 Comparative Example 7 82.4 10.35 28.4 45.1 Comparative Example 8 79.3 9.98 32.6 39.4 Comparative Example 9 83.8 11.20 27.5 42.2

Referring to Table 2, the lithium secondary batteries of Examples 1 to 10 using the non-aqueous electrolyte containing the compound represented by Formula 1 have excellent high-temperature cycle life performance and initial resistance compared to the lithium secondary batteries of Comparative Examples 1 to 9. It can be seen that is low, the rate of increase in resistance according to cycles is low, and the increase in volume according to cycles is small.

Claims (15)

lithium salt;
organic solvents; and
A non-aqueous electrolyte containing a compound represented by Formula 1 below:
[Formula 1]

In Formula 1, R ₁ and R ₂ are each independently a substituent selected from an alkyl group having 1 to 10 carbon atoms and an aryl group having 6 to 14 carbon atoms,
R ₃ , R ₄ , R ₅ , and R ₆ are each independently a substituent selected from the group consisting of hydrogen, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, and an aryl group having 6 to 14 carbon atoms,
In at least one substituent selected from R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ , at least one hydrogen is substituted with a halogen element selected from the group consisting of F, Br, Cl and I.
The method of claim 1,
The non-aqueous electrolyte solution wherein the compound represented by Formula 1 is contained in the non-aqueous electrolyte solution in an amount of 0.2% to 45% by weight.
The method of claim 1,
The non-aqueous electrolyte solution wherein the compound represented by Formula 1 is contained in the non-aqueous electrolyte solution in an amount of 5% to 30% by weight.
The method of claim 1,
The non-aqueous electrolyte solution wherein the halogen element is F.
The method of claim 1,
A non-aqueous electrolyte solution in which at least one hydrogen in at least one substituent selected from R ₃ , R ₄ , R ₅ , and R ₆ is substituted with a halogen element selected from the group consisting of F, Br, Cl, and I.
The method of claim 1,
wherein at least one substituent selected from R ₃ , R ₄ , R ₅ , and R ₆ is independently selected from a trifluoromethyl group and a trifluoromethoxy group.
The method of claim 1,
The non-aqueous electrolyte solution wherein at least one substituent of R ₃ , R ₄ , R ₅ , and R ₆ is a trifluoromethoxy group.
The method of claim 1,
The compound represented by Formula 1 is a non-aqueous electrolyte containing at least one selected from a compound represented by Formula 2 below and a compound represented by Formula 3 below:
[Formula 2]

[Formula 3]

In Formulas 2 and 3, R ₁ and R ₂ are each independently a substituent selected from an alkyl group having 1 to 10 carbon atoms and an aryl group having 6 to 14 carbon atoms.
The non-aqueous electrolyte solution according to claim 8, wherein in Formulas 2 and 3, R ₁ and R ₂ are methyl groups.
The method of claim 1,
The lithium salt is a non-aqueous electrolyte solution containing LiPF ₆ .
The method of claim 1,
The organic solvent is a non-aqueous electrolyte containing at least one selected from linear carbonates and cyclic carbonates.
The method of claim 1,
The organic solvent is a non-aqueous electrolyte solution containing a linear carbonate.
The method of claim 1,
The nonaqueous electrolyte solution is vinylene carbonate, vinylethylene carbonate, propane sultone, succinonitrile, adiponitrile, ethylene sulfate, propensultone, fluoroethylene carbonate, LiPO ₂ F ₂ , LiODFB (lithium difluorooxalatoborate), LiBOB (Lithium bis-(oxalato)borate), TMSPa (3-trimethoxysilanyl-propyl-N-aniline), TMSPi (Tris(trimethylsilyl) Phosphite), and LiBF ₄ - A non-aqueous electrolyte solution further comprising at least one additive selected from the group consisting of .
cathode;
an anode facing the cathode;
a separator interposed between the cathode and the anode; and
A lithium secondary battery comprising a non-aqueous electrolyte solution according to claim 1 .
The method according to claim 14, wherein the positive electrode current collector; And a positive electrode active material layer disposed on at least one surface of the positive electrode current collector;
The cathode active material layer includes a cathode active material,
The cathode active material is a lithium transition metal composite oxide, and contains 60 mol% or more of nickel based on the total number of moles of transition metals included in the lithium transition metal composite oxide.